I think that it would be better to have a hole in the center of the body of Holstow so as to easily remove the facet remaining in Holstrow without removing the center drill and push it out with a screwdriver or the like.

We were able to quietly drill a hole while injecting oil into the steel with a thickness of 4 mm using a desktop type exclusive machine. There was no spill of the blade, it was able to be made smoothly smoothly.